pain in ass

Author: maykulkarni

contest/TaskTorus.java

@@ -0,0 +1,84 @@
+package contest;
+
+import Utils.BladeReader;
+
+import java.io.PrintWriter;
+
+public class TaskTorus {
+    public void solve(int testNumber, BladeReader in, PrintWriter out) {
+        int size = in.nextInt();
+        int[][] mat = in.readIntMatrix(size, size);
+        int[][] ext = new int[(size << 1) - 1][(size << 1) - 1];
+        for (int i = 0; i < (size << 1) - 1; i++) {
+            for (int j = 0; j < (size << 1) - 1; j++) {
+                ext[i][j] = mat[i >= size ? (i - size) : i][j >= size ? (j - size) : j];
+            }
+        }
+
+//        System.out.println("Extended Matrix");
+//        new PrintMat(ext);
+        solve(ext, out, size);
+    }
+
+    private void solve(int[][] ext, PrintWriter out, int N) {
+        long maxSum = Long.MIN_VALUE;
+        int[][] costMatrix = getCostMatrix(ext);
+        for (int colStart = 0; colStart < N; colStart++) {
+            for (int colEnd = colStart; colEnd < colStart + N; colEnd++) {
+                int[] currentVector = getCurrentVector(ext, colStart, colEnd, costMatrix);
+                maxSum = Math.max(maxSum, kadane(currentVector, N));
+            }
+        }
+        out.println(maxSum);
+    }
+
+    private long kadane(int[] currentVector, int N) {
+        // Limit the rows
+        long max = Long.MIN_VALUE;
+        long sum = 0;
+        boolean vis[] = new boolean[currentVector.length];
+        for (int i = 0; i < currentVector.length; i++) {
+            if (i >= N && vis[i - N]) {
+                sum -= currentVector[i - N];
+                vis[i - N] = false;
+                for (int x = i - N + 1; x < i && !vis[x - 1]; x++)
+                    if (currentVector[x] < 0) {
+                        sum -= currentVector[x];
+                        vis[x] = false;
+                    }
+                max = Math.max(max, sum);
+            }
+            sum += currentVector[i];
+            vis[i] = true;
+            max = Math.max(max, sum);
+            if (sum < 0) {
+                sum = 0;
+                vis[i] = false;
+            }
+        }
+        return max;
+    }
+
+    private int[] getCurrentVector(int[][] ext, int colStart, int colEnd, int[][] costMatrix) {
+        int[] currentVector = new int[ext.length];
+        for (int i = 0; i < ext.length; i++) {
+            currentVector[i] = costMatrix[i][colEnd] - (colStart > 0 ? costMatrix[i][colStart - 1] : 0);
+        }
+//        System.out.println("Current Vector");
+//        System.out.println(Arrays.toString(currentVector));
+        return currentVector;
+    }
+
+    private int[][] getCostMatrix(int[][] ext) {
+        int[][] costMatrix = new int[ext.length][ext[0].length];
+        for (int i = 0; i < ext.length; i++) {
+            for (int j = 0; j < ext[0].length; j++) {
+                costMatrix[i][j] = (j > 0 ? costMatrix[i][j - 1] : 0) + ext[i][j];
+            }
+        }
+//        System.out.println("Cost Matrix");
+//        new PrintMat(costMatrix);
+        return costMatrix;
+    }
+}
+